1. Field of Invention
The present invention relates to control system and control method for starting an engine of a vehicle or the like, particularly to control of power supply to a starter motor in case of starter motor failure.
2. Description of Related Art
In recent years, with regard to vehicles including automobiles, increase in operability is required in addition to improvement in basic performance and safety thereof. Smart ignition is a function of improving operability.
The smart ignition is a function of starting an engine without using a mechanical key by a driver. A key held by the driver is a device which wirelessly communicates with a device mounted on a vehicle. For example, ID or the like is transmitted and checked between the key and the on-vehicle device, thereby confirming whether or not the key is a proper key. Then, the driver holding the proper key operates an operation unit, such as a switch or the like, provided in the vehicle, whereby the engine is started.
In a typical engine starter, first, two coils of a pull-in coil and a holding coil are energized before the rotation of a starter motor is begun. When a current passes through the pull-in coil and a magnet switch is turned on, a battery and the starter motor are connected. Further, a pinion moves, and a pinion gear of the starter motor and a ring gear of a flywheel of the engine are engaged, whereby the rotation of the starter motor can be transferred to the engine.
When a current is directly supplied from the battery to the starter motor and the starter motor begins to rotate, a crankshaft of the engine begins to rotate.
The rotational speed of the crankshaft of the engine is low shortly after the crankshaft begins to rotate. This state is referred to as a cranking state. In order to reliably start the engine, the cranking state needs to be maintained as long as possible.
In the realization of the smart ignition, the switching of the electric connection between the battery and each of various power loads, which has been performed by an operation of turning a mechanical key by the driver, needs to be performed using an electronic element, such as a relay, a semiconductor switch, or the like. That is, it is necessary to connect or disconnect the battery to/from an accessory (ACC) load, an ignition (IGN) load, the starter motor, or the like using an electronic element.
In the case where the switching among loads is performed using electronic elements, it is important to appropriately control switching timing. In particular, in the case where the engine is started by use of the aforementioned starter, the capability of starting the engine is reduced if the time for which the starter motor is being activated is short. Meanwhile, if the activation time is long, the starter motor may be overloaded. Accordingly, the time for which the starter motor is being activated needs to be appropriately controlled.
Various proposals have been made in order to perform power supply to the starter motor for an appropriate time. Japanese Patent Application Laid-open Publication No. 2002-221131 discloses a method of controlling the switching timing of a power source by determining ease in starting an engine based on the number of operations. Moreover, Japanese Patent Application Laid-open Publication No. 2002-221132 discloses a method of switching a power source by estimating an intention of a driver based on the operation of an operation unit by the driver.